Filtering systems and methods for voltage control

Abstract

A power factor correction (PFC) system includes an error control module that determines a first current demand based on a difference between a desired direct current (DC) voltage and a measured DC voltage. A filter module applies a filter to the first current demand to produce a second current demand. A weighting module (i) based on the difference, determines first and second weighting values for the first and second current demands, respectively, (ii) determines a third current demand based on the first current demand and the first weighting value, and (iii) determines a fourth current demand based on the second current demand and the second weighting value. A current demand module determines a final current demand based on the third current demand and fourth current demand. A current control module controls switching of a switch of a PFC device based on the final current demand.

What is claimed is: 
     
       1. A power factor correction (PFC) system comprising:
 an error control module that determines a first current demand based on a difference between a desired direct current (DC) voltage and a measured DC voltage; 
 a filter module that applies a filter to the first current demand to produce a second current demand; 
 a weighting module that (i) based on the difference, determines first and second weighting values for the first and second current demands, respectively, (ii) determines a third current demand based on the first current demand and the first weighting value, and (iii) determines a fourth current demand based on the second current demand and the second weighting value; 
 a current demand module that determines a final current demand based on the third current demand and fourth current demand; and 
 a current control module that controls switching of a switch of a PFC device based on the final current demand. 
 
     
     
       2. The PFC system of  claim 1  wherein further comprising a summation module that determines a fifth current demand based on a sum of the third and fourth current demands,
 wherein the current demand module applies a notch filter to the fifth current demand and determines the final current demand based on an output of the notch filter. 
 
     
     
       3. The PFC system of  claim 1  wherein, when the difference is less than a predetermined value, the weighting module sets the third current demand to zero. 
     
     
       4. The PFC system of  claim 1  wherein the weighting module:
 sets the third current demand based on the first current demand multiplied with the first weighting value; and 
 sets the fourth current demand based on the second current demand multiplied with the second weighting value. 
 
     
     
       5. The PFC system of  claim 1  wherein the filter module applies a low pass filter to the first current demand to produce the second current demand. 
     
     
       6. The PFC system of  claim 2  wherein the current demand module sets the final current demand based on the output of the notch filter multiplied by a value of a sinusoidal reference signal generated to be synchronous in phase and frequency with an input alternating current (AC) voltage. 
     
     
       7. The PFC system of  claim 2  further comprising a filter coefficients module that sets filter coefficients of the notch filter based on a frequency of an input alternating current (AC) voltage. 
     
     
       8. The PFC system of  claim 3  wherein, when the difference is less than the predetermined value, the weighting module further sets the fourth current demand equal to the second current demand. 
     
     
       9. The PFC system of  claim 3  wherein, when the difference is greater than the predetermined value, the weighting module increases the first weighting value and decreases the second weighting value. 
     
     
       10. The PFC system of  claim 3  wherein, when the difference is greater than the predetermined value, the weighting module increases the first weighting value as the difference increases and decreases the second weighting value as the difference increases. 
     
     
       11. A power factor correction (PFC) method comprising:
 determining a first current demand based on a difference between a desired direct current (DC) voltage and a measured DC voltage; 
 applying a filter to the first current demand to produce a second current demand; 
 based on the difference, determining first and second weighting values for the first and second current demands, respectively; 
 determining a third current demand based on the first current demand and the first weighting value; 
 determining a fourth current demand based on the second current demand and the second weighting value; 
 determining a final current demand based on the third current demand and fourth current demand; and 
 controlling switching of a switch of a PFC device based on the final current demand. 
 
     
     
       12. The PFC method of  claim 11  further comprising:
 determining a fifth current demand based on a sum of the third and fourth current demands; and 
 applying a notch filter to the fifth current demand, 
 wherein determining the final current demand includes determining the final current demand based on an output of the notch filter. 
 
     
     
       13. The PFC method of  claim 11  further comprising, when the difference is less than a predetermined value, setting the third current demand to zero. 
     
     
       14. The PFC method of  claim 11  further comprising:
 setting the third current demand based on the first current demand multiplied with the first weighting value; and 
 setting the fourth current demand based on the second current demand multiplied with the second weighting value. 
 
     
     
       15. The PFC method of  claim 11  wherein the filter is a low pass filter. 
     
     
       16. The PFC method of  claim 12  wherein determining the final current demand includes setting the final current demand based on the output of the notch filter multiplied by a value of a sinusoidal reference signal generated to be synchronous in phase and frequency with an input alternating current (AC) voltage. 
     
     
       17. The PFC method of  claim 12  further comprising setting filter coefficients of the notch filter based on a frequency of an input alternating current (AC) voltage. 
     
     
       18. The PFC method of  claim 13  further comprising, when the difference is less than the predetermined value, further setting the fourth current demand equal to the second current demand. 
     
     
       19. The PFC method of  claim 13  further comprising, when the difference is greater than the predetermined value, increasing the first weighting value and decreasing the second weighting value. 
     
     
       20. The PFC method of  claim 13  further comprising, when the difference is greater than the predetermined value, increasing the first weighting value as the difference increases and decreasing the second weighting value as the difference increases.